1. Field of the Invention
The present invention relates to a method for renewing an organic solvent containing a resin, a method for using the renewed organic solvent, and a method for producing an inkjet recording head by utilizing the method for renewing an organic solvent.
2. Description of the Related Art
Recently, the density of integrated circuits has been increasing, and accordingly semiconductor circuits have been becoming finer. Finer semiconductor circuits have been realized by, for example, reducing the wavelength of light used for exposing a pattern or employing an immersion method. When fine semiconductor circuits are produced, the intended performance of the semiconductor circuits may fail to be sufficiently achieved due to, for example, pinholes created in the pattern if the manufacturing process proceeds without removing a foreign substance present on a wafer surface. Thus, there is a stronger demand for a higher level of cleanliness of a wafer surface than before in order to form finer patterns.
In a semiconductor manufacturing process, photosensitive materials are used as, for example, a photoresist used for etching. In a general semiconductor manufacturing process, a photosensitive material is applied to the surface of a material in which a pattern is to be formed and then exposed to light to cause a chemical change. After the exposure, a resist pattern is formed by using a developing solution. Subsequently, the pattern is formed in the material under the photosensitive material by etching. The resist composed of the photosensitive material, which is no longer needed, is removed using a stripping solution.
In the steps of semiconductor manufacturing process, an organic solvent or an aqueous inorganic alkaline solution is commonly used for development or resist removal, and a small amount of the organic solvent or aqueous inorganic alkaline solution used for dissolving the photosensitive material remains as droplets on a wafer. The organic solvent or aqueous inorganic alkaline solution remaining on the wafer is rinsed away with water, which allows the wafer to be quickly dried.
The above-described semiconductor manufacturing process is also employed in manufacture of inkjet recording heads, in which nozzle portions are formed by repeating the steps of applying a photosensitive material to a silicon wafer, exposure, development, and etching.
An inkjet method is a method for recording an image, characters, and the like by ejecting fine ink droplets from a nozzle onto a recording medium (e.g., paper) using any of various operating principles. This method easily realizes high-speed recording, reduced mechanical noise, use of multiple colors and has advantageous features in that, for example, a highly flexible recording pattern can be formed and operations of development and fixation can be omitted, and thus has been increasingly widely used for various purposes. In particular, recently, there has been remarkable development in a full-color inkjet recording technique using water-based ink, which is capable of forming multi-colored images that are comparable to images produced using multi-color printing by an existing platemaking method and printing by color photography.
In response to a growing demand for improved recording properties such as high-definition recording and full-color recording, ink droplets have become finer and there has been a tendency for nozzles to become more densely arranged, and accordingly markedly high accuracy is required for the pattern. Therefore, if a photosensitive material that should have been removed when the nozzles were formed by utilizing a semiconductor manufacturing process remains, the photosensitive material may act as a foreign substance and block the ink-flow passage, which may lead to an adverse phenomenon such as clogging. The remaining photosensitive material may act also as a foreign substance in the steps of etching and exposure, which inhibits formation of an intended pattern. As a result, the designed performance of the inkjet recording head may fail to be sufficiently achieved.
As described above, in the step of removing a photosensitive material, such as development and resist removal, wafers are immersed in a developing-solution tank or a stripping-solution tank to remove the photosensitive material and subsequently immersed and rinsed in a pure water tank. In many cases, a developing solution or a stripping solution adhering to the wafer is replaced with pure water in this way in order to allow the wafer to be quickly dried and to remove the photosensitive material completely. As a result, the photosensitive material gradually accumulates in the developing-solution tank or stripping-solution tank as this wafer treatment proceeds. The photosensitive resin also accumulates in a rinsing tank at a lower concentration than in the solvent tank. This is because the pure water in the rinsing tank is replaced with the solvent containing a large amount of the photosensitive material adhered to the wafer.
When a certain amount or more of photosensitive material has accumulated as this wafer treatment proceeds, the photosensitive material cannot be completely dissolved in the developing-solution tank or the stripping-solution tank. In addition, during rinsing, the photosensitive material component contained in the developing solution or the stripping solution remaining on the wafer precipitates to form a residue. To avoid this, the developing solution, stripping solution, and pure water in the rinsing tank are replaced with new ones after treating certain wafers to remove the photosensitive material. Thus, the amount of photosensitive material contained in these tanks is reduced, which suppresses the formation of a foreign substance on the wafer.
However, the replaced waste liquid resulting from the accumulation of the photosensitive material is disposed of by incineration or the like, which may place a heavy load on the environment. Furthermore, generally, the developing solution and stripping solution used in these steps are expensive electronic grade chemicals, which disadvantageously increase the cost.
Accordingly, for example, in Japanese Patent Laid-Open No. 08-318263, a liquid used for development or resist removal is distilled to remove a photosensitive material and the distilled liquid is reused. This increases the number of wafers that can be processed using the same liquid in which a photosensitive material is dissolved.
In another example, in Japanese Patent Laid-Open No. 08-82937, rinse water is irradiated with ultraviolet rays to reduce the amount of organic materials contained in the rinse water and the resulting rinse water is reused.